This is part 7 of the AusIMM webinar on North American geology. The webinar can be viewed by following this link – https://www.ausimm.com/videos/community-event/south-west-wageoscience-society—digital-tech-talk-new-discoveries-in-the-structural-geology-mineralization–exploration-targeting-of-north-america/
This plan shows the tomography from Griffin et. al., 2013.
This was a good plan back in 2013. However, if there has been advances in structural geology definition, which is what we need to for targeting, there are no detailed structural geology images on the internet apart from mine. This is a pity because it hinders detailed/specific exploration targeting. These fuzzy seismic tomography plans are only good for very general exploration targeting.
That is the huge advantage my structural geology plans have over the above standard seismic tomography plans.
This plan is a preliminary structural geology plan but it clearly shows the ENE, WNW, NW and EW linear structures.
The biggest mines lie on the intersection of these structures.
The Carlin field is renowned as a dome and basin structural area and that is exactly the pattern one would get with this set of intersecting linears. Remember, we are down 300 km and these structures still propagate to the surface.
The same criteria applied in the Yilgarn of Western Australia where companies have been using my targeting plans derived from seismic tomography at 300 km depth for exploration targeting. The Yilgarn exploration targeting plans have been downloaded many times over the last 2 years 🙂 🙂 .
The link is – https://www.geotreks.com.au/work/giant-ring-structures/new-discoveries-correlate-with-watchorn-exploration-targeting-using-yilgarn-seismic-tomography-from-300-km-depth/
We will now look in more detail at exploration targeting using structural geology in the Goldstrike/Carlin/Bingham Canyon mining area (yellow rectangle).
11. Seismic tomography 300 km depth in the more local Goldstrike/Carlin/Bingham Canyon mining area.
This figure is of the more local Carlin/Bingham Canyon area .
The most obvious ring structure is to the centre-right and extends from the top-right through the centre and down to the bottom centre. It’s about 500 km in diameter. In the top centre-left is a very distinct small ring about 120 km in diameter.
These ring structures are clearer in the small insert at the bottom-right.
Generally speaking, these ring structures can be seen more clearly on the small-scale plans than large-scale plans where the structures are too much in your face.
There are also strong ENE structures with what looks like crenulation cleavage between them.
If this was a microscope slide, diamond drill core, an underground mine face map or surface field map, then it could only be described as brittle to semi-brittle structural geology.
Remember we are down at 300 km depth in the middle of what is currently considered the mobile mantle? It is not mobile otherwise these almost perfect rings and linear structures would not still exist.
The large ring can only have formed in the Late Heavy Bombardment 4.1 – 3.8 billion years ago (LHB, Hiesinger et al., 2000 and 2010) and it has not been destroyed!
The observations using this new structural geology gives a deeper understanding of the rheology of the layers of the Earth. This suggests that the Plate Tectonics mechanism and continent evolution needs a radical update!
This is the first time anyone has seen an ultra-detailed structural-geology plan for this area – make the most use of it for your exploration targeting!
The crenulation structures are sinistral in movement as shown by the flat S yellow line on the plane.
The biggest mines lie just inside or on the most obvious ring structures.
The Goldstrike mine lies on the small 120 km ring and the Carlin mine lies on the outer ring of the large 500 km ring. The Bingham Canyon mine lies on the inside edge of the median ring of the large ring structure. All of these mines lie on ENE, WNW, NE and NW linears.
All of these mines are huge disseminated deposits. Is this because the mineralisation has originated from 300 km depth – or deeper?
These mines are only tens of millions of years old compared with the ring structures age of > 3.8 billion years old. This suggests long continued and recent tectonic movement associated with the Pacific Plate subduction.
This is a similar exploration targeting plan (at the same depth) to one I did of the Yilgarn in Western Australia which is being used for detailed exploration targeting with great success.
Targeting can be refineded by using this plan with the following plan.
This is a very interesting and useful wormed plan.
I have enhanced this plan so that only the strongest crenulations stand out. Generally the largest mines lie on the strongest crenulations between the black ENE linear structures.
This in itself is an exploration targeting tool.
Targeting rationale. Follow the brightest ENE crenulations until they meet the rings or other mineralised geological structures. This gives the best chance of finding a new mining field. You draw on the targets!
Share this with your North American mining and exploration colleagues – you might get onto the big one!
Happy hunting
Bob Watchorn.